Pregnancy Due Date Calculator

This calculator estimates your due date and current week of pregnancy based on the date of your last menstrual period (LMP). It assumes a typical 28-day cycle and a 40-week (280-day) pregnancy.

These are estimates only and can differ from ultrasound dating or your doctor's assessment. Always rely on your healthcare provider for medical decisions.

How this pregnancy due date calculator works

Most due date calculators use the first day of your last menstrual period (LMP) and assume a 28-day cycle with ovulation around day 14. The classic Naegele's rule adds 280 days (40 weeks) to the adjusted LMP to estimate the due date.

This tool:

Lets you enter the first day of your last period (LMP)
Optionally adjusts for cycle length different from 28 days
Adds 280 days to estimate your due date
Estimates current gestational age and trimester

Every pregnancy is unique. Ultrasound dating, medical history and your doctor's assessment are more accurate than any online calculator. This tool is for general information only and is not a substitute for prenatal care.